1. Field of the Invention
The present invention relates to a recording device for an optical storage medium, and particularly to a method for dynamically adjusting a write power and a write strategy of an optical storage medium to optimize write parameters and a recording device therefor.
2. Description of Related Art
Commercialized writable optical storage media, for example, optical disks, can be categorized into many kinds, including CD-R, CD-RW, DVD-R, DVD+R, DVD-RW, DVD+RW and DVD-RAM. Dyes and materials used for these optical storage media are different in properties. Therefore, different optical storage media support different writing speeds, so do the write powers required for writing data into these optical storage media. Therefore, a general approach is to perform a so-called optimal power calibration (OPC) at a power calibration area (PCA) in an optical storage medium before writing data therein. In other words, it is a process of writing test data at a test area, then reading test data and assessing the signal quality thereof, thus finding out an optimal write power.
FIG. 1 is a flow chart illustrating a conventional method for calibrating an optimal write power. Referring to FIG. 1, at step S10, an optical disk is loaded in the recording device, then at step S11, the recording device determines an optimal write strategy from a plurality of pre-stored write strategies according to the optical storage medium, wherein the pre-stored write strategies are either pre-stored in the optical disk by an optical disk manufacturer or pre-stored in a memory means of the recording device by a recording device manufacturer. At step S12, the recording device uses a plurality of write powers to write test data into the test area of the optical disk incorporating with the optimal write strategy. At step S13, an optimal write power is determined from the test write powers according to test data read out from the test area. Finally, at step S14, the recording device writes data into the optical disk with the optimal write strategy and the optimal write power.
FIG. 2 is a flow chart illustrating another conventional method for calibrating an optimal write power, which is applied with a constant angular velocity (CAV) writing method. Referring to FIG. 2, steps S20 to S24 are the same as steps S10 to S14 as shown in FIG. 1. Because of the CAV writing method, writing speeds are different between an inner track and an outer track of an optical disk. Using a same write strategy for both inner tracks and outer tracks is likely to cause a writing failure. Therefore, an optical disk is usually divided into many zones. The first zone to be written uses a write strategy determined from those pre-stored write strategies according to the optical disk. The other zones use optimal write strategies obtained from adjusting the optimal strategy the first zone used. Herein, the pre-stored write strategies are pre-stored in the optical disk or a memory means of the recording device.
Continue referring to FIG. 2, at step S25, judges whether it reaches the next zone, if it does not, then go back to step S24; if it does, then proceed with step S26, incorporating with the present zone, the optimal write strategy of step S24 is adjusted and then substitute for the previous write strategy, then perform an optimal write power calibration, wherein the optimal write strategy is adjusted according to the previous write strategy and the zones to be written, rather than an instantly dynamic adjustment; then write data till all data are written in.
Furthermore, another approach of the CAV writing method is pre-storing the write strategies for all the zones into a memory means of the recording device. Which zone is to be written is judged according to the recording device. Thereafter, the corresponding write strategy optimal for the given zone is read out and then the optimal write power test is performed.
The process of writing data into an optical disk is actually forming a plurality of pits or marks which present data. Forms of the pits or marks can be changed by changing a combination between write strategies and write powers. FIGS. 3A and 3B respectively illustrate write strategies for CD-R and CD-RW. Referring to FIGS. 3A and 3B, the digital data to be written into the optical disk have to be encoded, that is an eight-to-fourteen modulation (EFM). The encoded EFM signals are written into the optical disk by an optical pickup head. As shown in FIG. 3A, a write strategy having parameters including Td, Tp and Tf is adapted for writing an optical disk of CD-R; and as shown in FIG. 3B, a write strategy having parameters including Td, Tp, Tf and Tm is adapted for writing an optical disk of CD-RW. Defining a unit time of a channel clock signal as T, T has a frequency of 4.32 MHz, so 1T is equal to 230 ns. Optical disks of DVD-R/RW, DVD+R/RW and DVD-RAM have more complicated definitions of parameters.
The optical pickup head has a laser diode (LD) for providing a light beam to the optical disk. As the writing speed is relatively low, the LD has a response speed faster than the speed that the encoded data being transmitted to the optical pickup head. Therefore, the forms of the pits or marks can be changed by changing the write powers. However, as the writing speed is relatively high, the response speed of the LD is relatively close to the 3T frequency of the encoded data. Once the response speed of the LD reaches its limit, changing the write powers will not change the forms of the pits or marks.
The above-described two conventional technologies can not instantly and dynamically adjust write strategies and write powers. Therefore, they can not readjust the responsive features of all of the pickup heads by adjusting the write strategies for obtaining better writing qualities.